Journal Article

FZJ-2021-05600

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png P removal from Si by Si-Ca-Al alloying-leaching refining: Effect of Al and the CaAl2Si2 phase

Zhu, M. ; Yue, S. ; Wu, G.FZJ* ; Tang, K. ; Xu, Y. ; Safarian, J.

2021
Elsevier Science Amsterdam [u.a.]

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Please use a persistent id in citations: doi:10.1016/j.seppur.2021.118675  doi:10.34734/FZJ-2021-05600

Abstract: Phosphorus (P) is a critical impurity in metallurgical-grade Si that needed to be removed for solar-grade Si production. The Si-Ca-Al-P system is one of the most crucial alloy systems for Si refining, where P can be separated by either the Si-Al solvent refining or the Si-Ca alloying-leaching process. In this work, a series of Si-Ca-Al alloys were obtained to investigate the role of alloy composition and the CaAl2Si2 phase in P segregation and separation. The used alumina crucible led to heavy Al contamination and resulted in unexpected Si-Ca-Al alloy compositions. CaAl2Si2 and CaSi2 were found as the main precipitates, and relatively higher P content was detected in the CaAl2Si2 phase. Leaching experiments indicate that P removal degree increases with increasing Ca/Al ratio and increasing total alloying amount (Ca + Al). Effects of alloy composition were further analyzed by statistical methods, which indicates Ca firmly plays a strong, positive, and monotonic role in P removal while no strong attraction between Al and P. Theoretical P removal model for the Si-Ca-Al system was established and in good agreement with measured results. Interaction coefficients of Ca and Al to P were fitted as and , which further confirms Ca is the essential driving force for P segregation. Finally, the possibility of P solid solution formation was verified by first-principle simulations that both CaAl2Si2 and CaSi2 are able to dissolve P, especially through the Si site, but the CaAl2Si2 phase is more favourable for P dissolution than CaSi2, which explains the reason of the often detected high P content in CaAl2Si2.

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Contributing Institute(s):

1. Werkstoffstruktur und -eigenschaften (IEK-2)

Research Program(s):

1. 1231 - Electrochemistry for Hydrogen (POF4-123) (POF4-123)

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Database coverage:
; ; ; Clarivate Analytics Master Journal List ; Current Contents - Engineering, Computing and Technology ; Ebsco Academic Search ; Essential Science Indicators ; IF >= 5 ; JCR ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection

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